class Solution {
public:
    int numDecodings(string s)
    {
        int n = s.size();
        vector<int> dp(n + 1);
        dp[0] = 1;
        dp[1] = s[1 - 1] != '0';

        for (int i = 2; i <= n; i++)
        {
            if (s[i - 1] != '0') dp[i] += dp[i - 1];
            int tmp = (s[i - 2] - '0') * 10 + (s[i - 1] - '0');
            if (tmp >= 10 && tmp <= 26) dp[i] += dp[i - 2];
        }
        return dp[n];
    }
};

class Solution {
public:
    int uniquePaths(int m, int n)
    {
        vector<vector<int>> dp(m + 1, vector<int>(n + 1, 0));
        dp[0][1] = 1;
        for (int i = 1; i <= m; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
            }
        }
        return dp[m][n];
    }
};

class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid)
    {
        int m = obstacleGrid.size(), n = obstacleGrid[0].size();
        vector<vector<int>> dp(m + 1, vector<int>(n + 1));
        dp[0][1] = 1;
        for (int i = 1; i <= m; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                if (obstacleGrid[i - 1][j - 1] == 1) dp[i][j] = 0;
                else dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
            }
        }
        return dp[m][n];
    }
};